1. Field of the Invention
This invention relates to a cable-entry seal for use with multiple-contact connector plugs such as are used with multiconductor seismic land cables.
2. Discussion of the Prior Art
In seismic exploration on land, many hundreds of acoustic detectors are emplaced upon the ground along a line of survey. The detectors are connected to a multichannel recording unit where the seismic signals from the various detectors are processed and recorded, usually on magnetic tape.
Seismic signals from the detectors are transmitted to the recordintg unit through long multiconductor cables. The number of conductors contained within a cable varies as the number of detectors to be serviced. Fifty to two hundred conductor pairs enclosed by an outer flexible jacket are commonly used. Because the number of conductors per cable varies somewhat, so also do the physical sizes of the cables vary. Typically the outside cable diameter may range from well under one-half inch to nearly one inch.
The cable laid out at any given time may extend for two miles or more. Necessarily therefore, the total cable is divided into shorter more readily manageable sections 100 to 200 feet long. The cable sections are terminated at each end by mating multicontact connectors. The connectors are generally non-polarized, hermaphroditic devices so that either end of any cable section will mate with any other cable section.
Multicontact connectors present two problems. First, mating connectors are physically very difficult to couple and uncouple because of the friction offered by the several hundred spring-metal contacts that must be securely mated. The two mating connector assemblies must be securely latched in place and must be reasonably waterproof.
Second, at the cable entry port where the multiconductor cable enters the body of the plug, a water-tight seal must be created around the cable and additionally the cable must be properly anchored into the plug. Usually, some form of rubber or Neoprene packing is compressed around the cable, in a packing box, by a gland nut. Often, when the packing is tight enough to anchor the cable and to form a water-tight seal, the packing extrudes between the collar of the gland nut and the cable jacket. Further, since many differently-sized cables are in general use, a large inventory of differently-sized packing material must be maintained. Descriptions of typical multicontact connectors used for seismic operations may be found in U.S. Pat. Nos. 4,166,663; 2,987,691; 3,086,188; 3,745,511 and Canadian Patent No. 881,128; as well as co-pending U.S. patent application Ser. No. 328,037 assigned to the assignee of this invention.